Manufacture of impregnated fiber articles



Patented luneza, 1936 UNITED STATES IKPBEGNATED ARTICLES 11 George a. Riehter and Hilton 0. Schur, Berlin, N. IL, anignars to Brown Company, Berlin, N. E, a corporation of Maine U cated, it is sometimes desirable to impregnate them with materials which impart water-repellency and other valuable characteristics thereto.

"persed, fusible waterproofing agent.

For instance, it may be desired to impregnate them, with heat-fusible, solid, waterproofing agents, such as asphalt, waxes, resins, or the like.

A convenient and economical way to impregnate 'fiber articles in a porous state with such agents is to treat them with water dispersions of these agents, and thento dry them under conditions to fuse the dispersed particles.

In accordance with the present invention, we associate regenerated cellulose, as well asa solid,

6 heat-fused, waterproofing agent, with the fiber article. The regenerated cellulose may be associated with the fiber article while largely preserving its porosity before the article is subjected t6 impregnation with the aqueous medium con-f taining the dispersed, fusible waterproofing agent. n the other hand, the article may be impregnated with a mixture of viscose and dis- When the article is then dried, it may besubiected to a sufliciently elevated drying temperature to fuse .the dispersedparticles and thus to produce a ,contmuous water-repellent phase enveloping the,

regenerated cellulose phase. Because of the incrtnessof the regenerated cellulose phase, it is not affected by thefusion and flow of the solid waterproofing material. Fiber articles, such as papers or felts, thus made are characterized by being doubly reinforced against being ruptured or disintegrated in the presence of water. Thus,

, should the phase of water-repellent material become cracked, abraded, or otherwise iniured so as to permit water to enter-into the article, the

phase of regenerated cellulose, which is also water-insoluble and which is not so readily disrupted or broken as the first-named phase, lends suiilcient' reinforcement to the fiber article to keep it intact even-under considerable stress and despite the entrance of water thereinto and/or the presence of water thereabout. The Mix,

' that papersmade in accordance with our invention can be soaked in water fordays and yet be preserved intact and of highstrength.

Inasmuch as there are various ways of case'- ciating' regenerated cellulose with fiber artlcla. -the present application is intended to cover broadly the association of regenerated with fiber articles, followed by the impregnation of. such articles with the aqueous media containlog the dispersed, fusible waterproofing agents, irrespective of the cellulose derivative used as the source of the regenerated cellulose or of the formation of the regenerated cellulose in the bulk fiber or pulp from which the article is to be fabricated or in the'aIready-fabricated fiber article. While-it is possible to employ nitrocellu- Application. September 23, 1932, Serial Nee-634,564

, 4 Claims. (Ciel-r0 After cellulose fiber articles have been fabri lose or other cellulose derivatives and toregencrate cellulose therefrom by the use of suitable the article may first be'form'ed, then impregnated with a; solution of viscose, and then treated with the cellulose-regenerating agent.v It is of advantage, however, to proceed as described in patent applications Serial No. 494,185, fi1ed November 7, 1930, by George A. Richter and Mil- .ton O. Schur (now Patent No. 1,856,114, dated May 3, 1932) and Serial No. 494,207, filed Novemher "I, 1930, by Milton O. Schur (now Patent No.

l,880,2 86, dated October 4, 1932), as those procedures have been found to be economical and f to lead to excellent results. According to the first-mentioned application, the cellulose-regencrating agent is applied to the article before it is treated with the viscose solution, as it has been found that the cellulose is regenerated as a more or less continuous phase throughout the fibrous structure. In the case of aflpaper, it is desirable to add a cellulose-regenerating agent, such as alum, to the paper stock in the beater engine, to the head-box of the paper machine, or to the web while it is in its course on the paper machine "or after it has come off the paper machine, and to treat the paper containing the cellulose-regenerating agent with the viscose after 'it has come oil thepaper machine, as such a procedure avoids corrosion of the wire or cylinder, mould of the paper machine by the sulphide impurities always present in viscose, as well as deterioration of the felts and drier cloth oi the paper machine by the free alkali present inv the viscose. Accordin: to the second-mentionedapplication, the alkali contentof the viscose is largely or completely neutralized, whereupon it is applied to the pulp from which the fiber article is to be fabricated or to the fabricated fiber article, and the article then dried and/or heated to liberate regenerated cellulose. The volatilesulphur compounds resulting from neutralization of alkali in the vispulp containing but a very small quantity of regenerated cellulose can be drawn through a; bath of water-dispersed asphalt, waxes, resins, or

mixtures of such heat-fusible, solid water-proofing agents to produce a uniformly impregnated sheet which, when dried at elevated temperature,

acquires high water-repellency on account of the fusion and coalescence of the dispersed particles; The impregnated sheet may be .dried in any suitable way, for instance, as by passing over the usual steam-heated drier drums, which should be maintained at a temperature above the fusing point of the dispersed particles ofwaterproofing agent. A waterleaf web of fibers containing but a very small quantity of regenerated cellulose istransformed by impregnation with dispersed wax or the like and subsequent drying at elevated temperature into a product having many of the characteristics of parchment paper. Our novel papers have an important advantage over parchment papers in that they do not take up water as readily and are hence to be preferred'for such uses as fabrication into bags or sacks,'designed to hold wet or moist materials, such as coal. I

The fibrousstructure of the articles of the present invention is characterized by the individual fibers carrying thin coatings of regenerated cellulose which keep'the fibers strongly bonded together, especially when the cellulose-is regenerated as a more or less continuous phase. The

still capable of taking up considerable quantities of dispersed waterproofing agent from the aqueous medium, for instance, considerably more dispersed waterproofing agent than its content of regenerated cellulose. The amount of waterproofing agent present in the finalproduct will depend upon the density of the original web. In

some instances, however, we may advantageously impregnatethe fiber article with a mixture of viscoseiand nispers'ed, fusible waterproofing material,-as" hereinbefore' indicated. For instance,

asdisclose'd in our application Serial No. 631,497, filed Sept. 2,-1932 (now Patent No. 1,971,274,

. dated August 21, 1934), a paper mayadvanticles. f The mixture" of viscose and wax-emulsion tageously be impregnated with a composition comprising viscose and an aqueous paraflin wax emulsion. If'desired, the mixed composition may contain another sizing agent, such as rosin size or other soap. The rosin size or-other soap may,

sion. The impregnated paper may "be dried'in:

the usual manner-on steam-heated drie'r'drums, which serve additionally to cause more or less flushing and coalescence of the dispersed wax parmay, if desired, be added to the bulk papermaking stoclr ih the-beater engine and undergo precipitatio'n" and iixati'on on the fibers through the action fthere'upon of alum'or equivalent acid salt or other acid i'ea'geiih bei'ore the stock is delivered to therpblfirmaking machine. The mixed composition maw in"fact, be'applied to the stock at any: :su'i'table stage of paper-making, i begin-' ning with the .bulk stock in the beater engine,

or to a prefabricated paper'sheet. Dispersions of fusiblewaterproofing material, including 'ticle, and fusing'the dispersed particles of waterproofing material therein.

applied to paper at any suitable stage of its manufacture, or to a prefabricated paper sheet. There are instances when such a mixed composition maybe used to advantage in fiber articles other than paper. For instance, fiber tubes are 5 sometimes made my convoluting a wet web of paper or paper pulp on a mandrel until the desired wall thickness has been reached, removing the tube from the mandrel, and drying it at elevated temperature. The application of a mixture. of viscose and water-dispersed asphalt or similar fusible waterproofing material might well be made to the fibrous web before it is convoluted into tubular form, whereupon the tube may be dried at a sufilciently elevated temperature to fuse the asphalt particles or similar waterproofing material. In such case, too, the aqueous dispersion of asphalt may be stabilized by soap, colloidal clay, or other hydrophilic colloids well known to those skilled in theart.

By the expression impregnating with an aqueous mediumcontaining a dispersed, heat-fusible, waterproofing agen as used in the appended claims, we mean to include-not only procedures whichresult in the agent being carried clear 25 through the porous fiber article by the aqueous medium, but also procedures by which only partial or surface penetration of the article is accomplished or by which the aqueous medium is caused to pass through the article while the agent 30 is deposited or filtered out on the surface as a coating with little penetration into the body of the article.

We claim:

1. A process which comprises introducing re- 85 generated cellulose throughout a porous fiber article while substantially preserving its porosity, impregnating the article throughout with an aqueous dispersion of heat-fusible, solid waterproofing material, and drying the impregnated article at a sufficiently elevated temperature to fuse the dispersed particles of waterproofing material.

,2. A process which comprises introducing regenerated cellulose throughout a waterleaf web of paper while substantially preserving its porosity, impregnating the paper throughout with an aqueous dispersion'of heat-fusible, solid waterproofing material, drying the impregnated ar- 3. A process which comprises introducing regenerated cellulose throughout a porous fiber article while substantially preserving its porosity,

submersing thearticle in a bath of water-dispersed, heat-fusible, solid waterproofing agent to impregnate said article with said dispersed particles, and drying the impregnatedarticle at a suificiently elevated temperature to fuse the dispersed particles.

4. A processwhich comprises introducing not more/ than about 1% regenerated cellulose throughouta'waterleaf web of paper, thereby substantially preserving its porosity, submersing 'the paper' in a 'bath of'waterdispersed, heatfusible; solidwaterproofing agent to impregnate said paper with said dispersed particles, and drying the impregnated .paper at a sufliciently elevated temperature to fuse the dispersed particles. 'GEORGE A. RICHTER.

- 'MILTON O. SCHUR. 

